Catalyst for polymerization of conjugated diene and method of polymerization conjugated diene using the catalyst, rubber composition for tires, and rubber composition for golf balls

ABSTRACT

[Subject] a catalyst for polymerization of conjugated diene is provided, which facilitates manufacture of a conjugated diene polymer with a high 1,4-cis structure content, leaves less aluminum residue on polymerization, and has high activity. A method of manufacturing conjugated diene polymers using the catalyst is also provided. 
     [Solution] A catalyst for polymerization of conjugated diene comprises (A) an yttrium compound; (B) an ionic compound including a non-coordinate anion and a cation; and (C) an organometallic compound including an element selected from the groups 2, 12 and 13 of the periodic table.

FIELD OF THE INVENTION

The present invention relates to a catalyst for polymerization ofconjugated diene with a high 1,4-cis structure content, and method ofmanufacturing conjugated diene polymers using the catalyst. It alsorelates to a rubber composition for tires having excellent abrasionresistance and flex crack-growth endurance and improved heat radiation,and a rubber composition for golf balls having appropriate hardnesstogether with high rebound and excellent processability.

BACKGROUND OF THE INVENTION

Catalysts for polymerization of conjugated dienes such as a1,3-butadiene and an isoprene have been conventionally proposed a lotand some of them have been industrialized. For example, a method ofmanufacturing conjugated diene polymers with a high cis-1,4 structureoften uses a compound of titanium, cobalt, nickel or neodymium and anorganoaluminum in combination.

The use of a group-3 element of the periodic table as a catalyst forpolymerization of conjugated dienes has been well known, and variouspolymerization methods have been proposed until now. For example,JP-A6-228221 discloses a solid catalyst holding a support for(co)polymerization of conjugated dienes, which holds a compound of atleast one of metals having atomic numbers 57-71, 92 on a support. Anyttrium catalyst having an atomic number 39 is hardly described however.

JP-A 7-70143 discloses an organometallic complex including yttrium (Y),neodymium (Nd) or praseodymium (Pr) and a group-13 element. No exampleof polymerization of yttrium complexes is described however.

JP-A 7-268013 describes a catalytic system including neodymium (Nd),praseodymium (Pr), dysprosium (Dy), lanthanum (La), gadolinium (Ga) andyttrium (Y) in combination with an aluminum alkyl and a trialkylderivative of boron. It exemplifies methods of polymerizing conjugateddiene compounds, which are though limited in neodymium and praseodymium.

JP-A 8-325330, JP-A 9-151219, JP-A 10-60174, JP-A 11-217465 and JP-A11-222536 exemplify yttrium as a metal to be turned into a catalyst formanufacture of a cis-1,4-polybutadiene but fail to provide any specifiedexample using an yttrium catalyst.

JP-A 2003-226721 discloses a method of manufacturing acis-1,4-polybutadiene in the presence of a catalyst, which is a compoundof an element selected from the group consisting of scandium, yttrium,lanthanides and actinides. No specified example using an yttriumcatalyst is shown, however, and exemplification of the method ofpolymerizing conjugated diene compounds is limited in neodymium andpraseodymium.

A Polybutadiene has a bonded portion (1,4-structure) generated frompolymerization at the 1,4-site and a bonded portion (1,2-structure)generated from polymerization at the 1,2-site, which coexist in amolecular chain as the so-called microstructure. The 1,4-structure isfurther classified into two: a cis structure and a trans structure. Onthe other hand, the 1,2-structure is structured to have a vinyl group ina side chain.

As known, depending on polymerization catalysts and polymerizationconditions, polybutadienes different in the above microstructure areproduced and employed in various uses in accordance with theirproperties.

For the purpose of improving the heat radiation and abrasion resistanceof tires, blending a polybutadiene rubber (BR) in natural rubber and soforth is widely performed, and various BRs are proposed. For example,JP-A 7-118443 discloses a BR having a weight average molecular weight of500,000-750,000, a molecular weight distribution of 1.5-3.0, and aninherent viscosity of 90 or more. JP-A2001-247721 discloses a BR havinga cis content of 95% or more and a molecular weight distribution of3.5-6.0.

In a rubber composition for golf balls, particularly, a high-cispolybutadiene with a relatively narrow molecular weight distribution anda high molecular linearity has a property excellent in abrasionresistance, resistance to heat radiation, and rebound resilience. As anindex of linearity of high-cis polybutadienes with almost similarmolecular weight distributions, Tcp/ML₁₊₄ is used. Tcp indicates thedegree of molecular entanglement in a thick solution. The lager theTcp/ML₁₊₄, the smaller the branch degree and the larger the linearityis.

Golf balls are classified into a thread wound type and a solid type. Thesolid center in the thread wound ball, as well as the solid ball,conventionally includes a rubber base material such as a polybutadiene,and a monomer having an unsaturated bond, such as an unsaturated metalcarboxylate, compounded therein as a crosslinking coagent. A peroxideand a metal oxide are also compounded therein.

The polybutadiene used as the rubber base material of golf balls isgenerally required to have high rebound and excellent processability. Ahigher Mooney viscosity improves the rebound but worsens theprocessability while a wider molecular weight distribution improves theprocessability but lowers the rebound in an antinomy relation.

For the purpose of achieving the compatibility of processability andrebound, improvements in polybutadiene rubber have been tried andvarious proposals have been provided. For example, JP-A 63-275356 andJP-A 2-177973 disclose polybutadienes having a high Mooney viscosity anda wide molecular weight distribution and synthesized in the presence ofa Ni-based catalyst. JP-A 6-80123 discloses a method that uses apolybutadiene having a low Mooney viscosity blended with a polybutadienehaving a high Mooney viscosity.

JP-A 7-268132 discloses the use of a polybutadiene, having a cis contentof 97% or more and modified with a tin compound, as a rubber basematerial for golf balls. This remains unchanged in the crosslinkdensity, however, compared to the conventional high-cis polybutadiene,and accordingly an improvement is desired in durability.

The Inventor et al. disclose in JP-A 2001-40040 that a polybutadieneappropriately having the 1,2-content can be used in long-carry golfballs.

SUMMARY OF THE INVENTION Subject to be Solved by the Invention

The conventional titanium-, cobalt- and nickel-based catalysts forpolymerization of conjugated diene have a problem because the 1,4-cisstructure content is low. A neodymium catalyst system containing nomethyl alumoxane promoter has low activity on polymerization while aneodymium catalyst system containing a methyl alumoxane promoter leavesan aluminum residue a lot after polymerization disadvantageously.

In the rubber composition for tires, generally BR is excellent in heatradiation, abrasion resistance and rebound resilience but poor inchip-cut property and flex crack-growth endurance. In this case, awidened molecular weight distribution or branching may improve the flexcrack-growth endurance but lower the heat radiation and abrasionresistance disadvantageously.

In the rubber composition for golf balls, those having higher reboundthan usual and excellent in processability are eagerly desired.

The present invention has a first object to provide a catalyst forpolymerization of conjugated diene polymers, which facilitatesmanufacture of a conjugated diene polymer with a high 1,4-cis structurecontent, leaves less aluminum residue on polymerization, and has highactivity. A method of manufacturing conjugated diene polymers using thecatalyst is also provided.

The present invention has a second object to provide a rubbercomposition for tires, having excellent abrasion resistance and flexcrack-growth endurance and improved heat radiation.

The present invention has a third object to provide a rubber compositionfor golf balls, having maintained hardness and high rebound togetherwith excellent processability.

Means for Solving the Subject

To achieve the first object, the present invention provides a catalystfor polymerization of conjugated diene, comprising: (A) an yttriumcompound; (B) an ionic compound including a non-coordinate anion and acation; and (C) an organometallic compound including an element selectedfrom the groups 2, 12 and 13 of the periodic table.

The catalyst for polymerization of conjugated diene according to thepresent invention comprises the yttrium compound. Accordingly, it has ahigher 1,4-cis structure content compared to the conventional titanium-,cobalt- and nickel-based catalysts for polymerization of conjugateddiene; higher activity on polymerization compared to the neodymiumcatalytic system containing no methyl alumoxane co-catalyst; and lessaluminum residue after polymerization compared to the neodymiumcatalytic system containing a methyl alumoxane co-catalyst. The catalystfor polymerization of conjugated diene according to the presentinvention has higher activity on polymerization, larger ease ofhandling, and lower catalyst cost compared to catalyst systems of themetallocene type (Nd, Sm, Gd).

In the catalyst for polymerization of conjugated diene polymersaccording to the present invention, preferably, the (A) yttrium compoundcomprises an yttrium compound having a bulky ligand shown in ChemicalFormula 2.

where R₁, R₂, R₃ denote hydrogen or a substituent having 1-12 carbonatoms; O denotes an oxygen atom; and Y denotes an yttrium atom.

In the catalyst for polymerization of conjugated diene according to thepresent invention, preferably, the conjugated diene polymers include acis-1,4-polybutadiene having 90% or more of a cis-1,4 structure.

The present invention also provides a method of manufacturing conjugateddiene polymers, comprising polymerizing a conjugated diene using thecatalyst described above. In the method, preferably, the step ofpolymerizing the conjugated diene polymer includes adjusting a molecularweight by a compound selected from (1) hydrogen, (2) a hydrogenatedmetallic compound and (3) a hydrogenated organometallic compound. Inthis case, preferably, the hydrogenated organometallic compoundcomprises a dialkyl aluminum hydride.

To achieve the second object, the present invention provides a rubbercomposition for tires, comprising: (a) 10-90% by weight of a high-cispolybutadiene derived from polymerization of 1,3-butadiene in thepresence of a catalyst comprising (A) an yttrium compound, (B) an ioniccompound including a non-coordinate anion and a cation, and (C) anorganometallic compound including an element selected from the groups 2,12, 13 of the periodic table; (b) 90-10% by weight of a diene-basedrubber other than the (a) high-cis polybutadiene; and (c) 1-100 parts byweight of a rubber reinforcer mixed in 100 parts by weight of a rubbercomponent (a)+(b).

To achieve the third object, the present invention provides a rubbercomposition for golf balls, comprising: a base polymer including ahigh-cis polybutadiene derived from polymerization of 1,3-butadiene inthe presence of a catalyst comprising (A) an yttrium compound, (B) anionic compound including a non-coordinate anion and a cation, and (C) anorganometallic compound including an element selected from the groups 2,12, 13 of the periodic table; and 10-50 parts by weight of acrosslinking coagent mixed in 100 parts by weight of the base polymer.

In the rubber composition for tires and the rubber composition for golfballs according to the present invention, preferably, the high-cispolybutadiene has a molecular weight adjusted by a compound selectedfrom (1) hydrogen, (2) a hydrogenated metallic compound and (3) ahydrogenated organometallic compound. In addition, preferably, thehydrogenated organometallic compound comprises a dialkyl aluminumhydride. In the rubber composition for tires and the rubber compositionfor golf balls according to the present invention, preferably, thehigh-cis polybutadiene comprises a cis-1,4-polybutadiene having 90% ormore of a cis-1, 4 structure.

EFFECTS OF THE INVENTION

Thus, the present invention is possible to provide a catalyst forpolymerization of conjugated diene, which facilitates manufacture of aconjugated diene polymer with a high 1,4-cis structure content, leavesless aluminum residue on polymerization, and has high activity, and amethod of manufacturing conjugated diene polymers using the catalyst.The present invention is also possible to provide a rubber compositionfor tires, having excellent abrasion resistance and flex crack-growthendurance and improved heat radiation. The present invention is furtherpossible to provide a rubber composition for golf balls, havingmaintained hardness and high rebound together with excellentprocessability.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferably usable examples of the yttrium compound of the (A) componentin the catalytic system of the present invention include salts andcomplexes of yttrium. Particularly preferable examples include salts ofyttrium such as yttrium trichloride, yttrium tribromide, yttriumtriiodide, yttrium nitrate, yttrium sulfate, yttrium trifluoromethanesulfonate, yttrium acetate, yttrium trifluoro acetate, yttrium malonate,octylic acid (ethyl hexanoic acid) salt of yttrium, yttrium naphthenate,versatic acid salt of yttrium, and yttrium neodecanate; alkoxides suchas yttrium trimethoxide, yttrium triethoxide, yttrium triisopropoxide,yttrium tributoxide, and yttrium triphenoxide; organic yttrium compoundssuch as tris(acetylacetonate) yttrium, tris(hexane dionate) yttrium,tris(heptane dionate) yttrium, tris(dimethyl heptane dionate) yttrium,tris(tetramethyl heptane dionate) yttrium, tris (acetoacetate) yttrium,cyclopentadienyl yttrium dichloride, dicyclopentadienyl yttriumdichloride, and tricyclopenta dienyl yttrium; organobasic complexes suchas pyridine complexes of yttrium salt and picoline complexes of yttriumsalt; hydrates of yttrium salt; and alcohol complexes of yttrium salt.In particular, as the (A) component in the catalyst, an yttriumcarboxylate such as yttrium acetate, yttrium trifluoro acetate, yttriummalonate, octylic acid (ethyl hexanoic acid) salt of yttrium, yttriumnaphthenate, and yttrium neodecanate; or an yttrium compound such astris(acetylacetonate) yttrium, tris(hexanedionate) yttrium, tris(heptanedionate) yttrium, tris(dimethylheptanedionate) yttrium,tris(tetramethyl heptanedionate) yttrium, and tris (acetoacetate)yttrium may be used. This use is effective to achieve a higher cis-1,4content in conjugated diene polymers compared to the use of neodymiumcarboxylate.

An yttrium compound having a bulky ligand shown in Chemical Formula 3can be used.

where R₁, R₂, R₃ denote hydrogen or a substituent having 1-12 carbonatoms; O denotes an oxygen atom; and Y denotes an yttrium atom.

Specific examples of R₁, R₂, R₃ include hydrogen, methyl group, ethylgroup, vinyl group, n-propyl group, isopropyl group, 1-propenyl group,allyl group, n-butyl group, s-butyl group, isobutyl group, t-butylgroup, n-pentyl group, 1-methyl butyl group, 2-methyl butyl group,3-methyl butyl group, 1,1-dimethyl propyl group, 1,2-dimethyl propylgroup, 2,2-dimethyl propyl group, hexyl group, heptyl group, octylgroup, nonyl group, decyl group, undecyl group, dodecyl group,cyclohexyl group, methyl cyclohexyl group, ethyl cyclohexyl group,phenyl group, benzyl group, tolyl group, and phenethyl group. Further,they may contain hydroxyl group, carboxyl group, carbomethoxy group,carboethoxy group, amido group, amino group, alkoxy group, and phenoxygroup, which may be substituted at an arbitrary position.

As the above yttrium compound, a salt or complex of yttrium ispreferably used. Particularly preferable examples include yttriumcompounds such as tris(acetyl acetonate) yttrium, tris(hexane dionate)yttrium, tris (heptane dionate) yttrium, tris(dimethyl heptane dionate)yttrium, tris(trimethyl heptane dionate) yttrium, tris(tetra methylheptane dionate) yttrium, tris(penta methyl heptane dionate) yttrium,tris(hexa methyl heptane dionate) yttrium, and tris(acetoacetate)yttrium. In particular, the use of yttrium having such a bulky ligand asthe (A) component in the catalyst system is effective because theactivity is higher than when neodymium having a similarly bulky ligandis used.

The (B) component in the catalytic system of the present invention is anionic compound including a non-coordinate anion and a cation. In thiscase, examples of the non-coordinate anion include tetra (phenyl)borate, tetra (fluoro phenyl) borate, tetrakis(difluorophenyl) borate,tetrakis(trifluorophenyl) borate, tetrakis(tetrafluorophenyl) borate,tetrakis(pentafluorophenyl) borate, tetrakis(3,5-bis(trifluoromethyl)phenyl) borate, tetrakis(tetrafluoro methylphenyl) borate, tetra(tolyl) borate, tetra(xylyl) borate,triphenyl(pentafluorophenyl) borate,tris(pentafluorophenyl)phenylborate, tridecahydride-7,8-dicarbaundecaborate, tetrafluoro borate, and hexafluoro phosphate.

On the other hand, examples of the cation include carbonium cation,oxonium cation, ammonium cation, phosphonium cation, cycloheptatrienylcation, and ferrocenium cation.

Specific examples of the carbonium cation include triphenylcarboniumcation and tri-substituted carbonium cations such as tri-substitutedphenyl carbonium cation. Specific examples of the tri-substituted phenylcarbonium cation include tri(methylphenyl)carbonium cation andtri(dimethyl phenyl)carbonium cation.

Specific examples of the ammonium cation include trialkyl ammoniumcations such as trimethyl ammonium cation, triethyl ammonium cation,tripropyl ammonium cation, tributyl ammonium cation, and tri(n-butyl)ammonium cation; N,N-dialkyl anilinium cations such as N,N-dimethylanilinium cation, N,N-diethyl anilinium cation, andN,N-2,4,6-pentamethyl anilinium cation; and dialkyl ammonium cationssuch as di(i-propyl) ammonium cation, and dicyclohexyl ammonium cation.

Specific examples of the phosphonium cation include aryl phosphoniumcations such as triphenyl phosphonium cation, tetraphenyl phosphoniumcation, tri(methylphenyl)phosphonium cation,tetra(methylphenyl)phosphonium cation, tri(dimethyl phenyl)phosphoniumcation, and tetra(dimethylphenyl) phosphonium cation.

The ionic compound may preferably include a combination of anon-coordinate anion and a cation, arbitrarily selected from the aboveexamples.

In particular, preferable examples of the ionic compound includetriphenylcarbonium tetrakis(pentafluoro phenyl) borate,triphenylcarbonium tetrakis(fluorophenyl) borate, N,N-dimethyl aniliniumtetrakis(pentafluorophenyl) borate, and 1,1′-dimethylferroceniumtetrakis(pentafluoro phenyl)borate. The ionic compound may be employedsolely or in combination of two or more.

The (B) component may include alumoxane. Examples of the alumoxaneinclude a chain aluminoxane and a cyclic aluminoxane produced bybringing an organoaluminum compound into contact with a condensationagent and represented by a general formula (—Al(R′)O—)n. (R′ denotes ahydrocarbon group having 1-10 carbon atoms and including a halogen atomand/or an alkoxy group partly substituted; and n denotes the degree ofpolymerization, which is equal to 5 or more, preferably 10 or more).Examples of R′ include methyl, ethyl, propyl, and isobutyl groups. Themethyl group is preferable. Examples of the organoaluminum compound foruse in material of aluminoxane include trialkyl aluminum such astrimethyl aluminum, triethyl aluminum, and tirisobutyl aluminum, andmixtures thereof.

Among those, the alumoxane including a mixture of trimethyl aluminum andtributyl aluminum as material may be employed suitably.

Examples of the condensation agent include water typically and any otheragents that allow for condensation reaction with the trialkyl aluminum,for example, water adsorbed on such as inorganic substance, and diol.

The (C) component in the catalytic system of the present invention is anorganometallic compound of an element in the group 2, 12, 13 of theperiodic table. In this case, examples of the organometallic compoundinclude organo magnesium, organozinc, and organoaluminum. Preferableexamples in these compounds include dialkyl magnesium, alkyl magnesiumchloride, alkyl magnesium bromide, dialkyl zinc, trialkyl aluminum,dialkyl aluminum chloride, dialkyl aluminum bromide, alkyl aluminumsesqui chloride, alkyl aluminum sesqui bromide, alkyl aluminumdichloride, and dialkyl aluminum hydride.

Specific compounds include alkyl magnesium halides such as methylmagnesium chloride, ethyl magnesium chloride, butyl magnesium chloride,hexyl magnesium chloride, octyl magnesium chloride, ethyl magnesiumbromide, butyl magnesium bromide, butyl magnesium iodide, and hexylmagnesium iodide.

Further examples include dialkyl magnesium such as dimethyl magnesium,diethyl magnesium, dibutyl magnesium, dihexyl magnesium, dioctylmagnesium, ethyl butyl magnesium, and ethyl hexyl magnesium.

Further examples include trialkyl zinc such as dimethyl zinc, diethylzinc, diisobutyl zinc, dihexyl zinc, dioctyl zinc, and didecyl zinc.

Further examples include trialkyl aluminum such as trimethyl aluminum,triethyl aluminum, triisobutyl aluminum, trihexyl aluminum, trioctylaluminum, and tridecyl aluminum.

Further examples include dialkyl aluminum chlorides such as dimethylaluminum chloride, and diethyl aluminum chloride; organoaluminum halidessuch as ethyl aluminum sesqui chloride, and ethyl aluminum dichloride;and hydrogenated organoaluminum compounds such as diethyl aluminumhydride, diisobutyl aluminum hydride, and ethyl aluminum hydride.

The element in the group 2, 12, 13 of the periodic table may be employedsolely or in combination of two or more.

A conjugated diene can be polymerized in the presence of theabove-described catalyst while the molecular weight of the resultantconjugated diene polymer can be adjusted with an agent, which mayinclude a compound selected from (1) hydrogen, (2) a hydrogenatedmetallic compound and (3) a hydrogenated organometallic compound.

Examples of the (2) hydrogenated metallic compound serving as themolecular weight adjusting agent of the present invention includelithium hydride, sodium hydride, potassium hydride, magnesium hydride,calcium hydride, borane, aluminum hydride, gallium hydride, silane,germane, lithiumborohydride, sodium borohydride, lithium aluminumhydride, and sodium aluminum hydride.

Examples of the (3) hydrogenated organometallic compound serving as themolecular weight adjusting agent of the present invention include alkylborane such as methyl borane, ethyl borane, butyl borane, and phenylborane; dialkyl borane such as dimethyl borane, diethyl borane, dipropylborane, dibutyl borane, and diphenyl borane; alkyl aluminum dihydridesuch as methyl aluminum dihydride, ethyl aluminum dihydride, propylaluminum dihydride, butyl aluminum dihydride, and phenyl aluminumdihydride; dialkyl aluminum hydride such as dimethyl aluminum hydride,diethyl aluminum hydride, dipropyl aluminum hydride, dibutyl aluminumhydride, and diphenyl aluminum hydride; silanes such as methyl silane,ethyl silane, propyl silane, butyl silane, phenyl silane, dimethylsilane, diethyl silane, dipropyl silane, dibutyl silane, diphenylsilane, trimethyl silane, triethyl silane, tripropyl silane, tributylsilane, and triphenyl silane; and germanes such as methyl germane, ethylgermane, propyl germane, butyl germane, phenyl germane, dimethylgermane, diethyl germane, dipropyl germane, dibutyl germane, diphenylgermane, trimethyl germane, triethyl germane, tripropyl germane,tributyl germane, and triphenyl germane.

Among those, diisobutyl aluminum hydride and diethyl aluminum hydrideare preferable, and diethyl aluminum hydride is particularly preferable.

The catalyst components can be added in any order not particularlylimited though they may be added in the following order.

(1) In an inactive organic solvent, in the presence or absence of aconjugated diene compound monomer to be polymerized, the (C) componentis added, then the (A) component and the (B) component are added in anyarbitrary order.

(2) In an inactive organic solvent, in the presence or absence of aconjugated diene compound monomer to be polymerized, the (C) componentis added, then the above-described molecular weight adjusting agent isadded, and finally the (A) component and the (B) component are added inany arbitrary order.

(3) In an inactive organic solvent, in the presence or absence of aconjugated diene compound monomer to be polymerized, the (A) componentis added, then the (C) component and the above-described molecularweight adjusting agent are added in any arbitrary order, and finally the(B) component is added.

(4) In an inactive organic solvent, in the presence or absence of aconjugated diene compound monomer to be polymerized, the (B) componentis added, then the (C) component and the above-described molecularweight adjusting agent are added in any arbitrary order, and finally the(A) component is added.

(5) In an inactive organic solvent, in the presence or absence of aconjugated diene compound monomer to be polymerized, the (C) componentis added, then the (A) component and the (B) component are added in anyarbitrary order, and finally the above-described molecular weightadjusting agent is added.

The components may be previously matured for use. In particular, it ispreferable to mature the (A) component and the (C) component.

The condition for maturing requires that, in an inactive solvent, in thepresence or absence of a conjugated diene compound monomer to bepolymerized, the (A) component is mixed with the (C) component. Thetemperature for maturing is −50 to 80° C., preferably −10 to 50° C. Thetime for maturing is 0.01-24 hours, preferably 0.05-5 hours, andparticularly 0.1-1 hour.

In the present invention each catalyst component may be held on aninorganic compound or an organic high molecular compound and used.

Examples of the conjugated diene compound monomer include 1,3-butadiene,isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethyl butadiene,2-methyl pentadiene, 4-methyl pentadiene, and 2,4-hexadiene. Inparticular, a conjugated diene compound monomer mainly including1,3-butadiene is preferable.

These monomer components may be employed solely or in combination of twoor more.

The conjugated diene compound monomer to be polymerized may comprise allor part of monomers. Where it comprises part of monomers, theabove-described contact mixture may be mixed with the remainder ofmonomers or the remainder of monomer solutions. In addition to theconjugated diene, it may contain olefin compounds such as ethylene,propylene, allene, 1-butene, 2-butene, 1,2-butadiene, pentene, cyclopentene, hexene, cyclohexene, octene, cyclooctadiene, cyclododecatriene, norbornene, and norobornadiene.

There is no restriction in polymerization methods. Applicable examplesinclude bulk polymerization in which the conjugated diene compoundmonomer such as 1,3-butadiene itself is used as a polymerizationsolvent, and solution polymerization. Examples of the solvent in thebulk polymerization include aliphatic hydrocarbon such as butane,pentane, hexane, and heptane; alicyclic hydrocarbon such ascyclopentane, and cyclohexane; aromatic hydrocarbon such as benzene,toluene, xylene, and ethyl benzene; the above-described olefincompounds; and olefin-based hydrocarbon such as cis-2-butene, andtrans-2-butene.

In particular, benzene, toluene, cyclohexane, and a mixture ofcis-2-butene and trans-2-butene are preferably used.

The temperature for polymerization falls preferably within a range of−30 to 150° C., particularly within a range of 30 to 100° C. The timefor polymerization falls preferably within a range of one minute to 12hours, particularly 5 minutes to 5 hours.

After polymerization is executed for a certain period of time, ifrequired, the polymerization chamber is subjected to releasing pressurefrom inside and post-treatments such as washing and drying.

The resultant conjugated diene polymer in the present invention maycomprise a cis-1,4-polybutadiene having a cis-1,4 structure by,preferably 90% or more, further preferably 92% or more, and particularly96% or more. The conjugated diene polymer is controlled to have [η] of,preferably 0.1-10, further preferably 1-7, and particularly 1.5-5.

In the rubber composition for tires according to the present invention,examples of the (b) diene-based rubber other than (a) include high-cispolybutadiene rubber, low-cis polybutadiene rubber (BR),emulsion-polymerized or solution-polymerized styrene butadiene rubber(SBR), natural rubber, polyisoprene rubber, ethylene propylene dienerubber (EPDM), nitrile rubber (NBR), butyl rubber (IIR), and chloroprenerubber (CR).

In addition, derivatives of these rubbers, for example, polybutadienerubbers modified with tin compounds, and the above rubbersepoxy-modified, silane-modified, and maleic acid-modified can beemployed. These rubbers may be employed solely or in combination of twoor more.

In the rubber composition for tires according to the present invention,examples of the (c) rubber reinforcer include inorganic reinforcers suchas various carbon blacks and white carbon, activated calcium carbonate,ultra-particulate magnesium silicate; and organic reinforcers such assyndiotactic 1,2-polybutadiene, polyethylene resin, polypropylene resin,high styrene resin, phenol resin, lignin, modified melanin resin,coumarone indene resin, and petroleum resin. Particularly preferableexamples include carbon black having a particle diameter less than 90 nmand dibutyl phthalate (DBR) oil absorption more than 70 ml/100 g, suchas FEF, FF, GPF, SAF, ISAF, SRF, HAF.

Preferably, the syndiotactic 1,2-polybutadiene has a melting pointhigher than 110° C. The syndiotactic 1,2-polybutadiene may be producedwith a suspension polymerization method described in JP-A 9-20811. Itcan be produced, in the presence of butadiene, using a catalyst,comprising: a matured liquid (A component) obtained by bringing a cobaltcompound, a group I-III organometallic compound or hydrogenated metalliccompound, and a compound selected from the group consisting of ketone,carboxylate, nitrile, sulfoxide, amide and phosphate into contact witheach other; and a compound (B component) selected from the groupconsisting of carbon disulfide, phenyl isothiocyanate, and xanthogenatecompounds. The melting point can be adjusted with a compound selectedfrom the group consisting of ketone, carboxylate, nitrile, sulfoxide,amide and phosphate to fall within, preferably 110-200° C., particularly130-160° C.

A solution polymerization method may also be employed with a catalyticsystem comprising soluble cobalt-organoaluminum compound-carbondisulfide-melting point adjusting agent.

The rubber composition for tires according to the present invention hasa mixture proportion of 100 parts by weight of the rubber component(a)+(b), composed of 10-90% by weight of the specific high-cispolybutadiene (a) and 90-10% by weight of the diene-based rubber (b)other than (a), to 1-100 parts by weight of the rubber reinforcer (c).

A preferable proportion is of 100 parts by weight of the rubbercomponent (a)+(b), composed of 20-80% by weight of the specific high-cispolybutadiene (a) and 80-20% by weight of the diene-based rubber (b)other than (a), to 5-80 parts by weight of a rubber reinforcer (c).

The rubber composition for tires according to the present invention canbe produced by kneading the components using a Banbury mixer, an openroll, a kneader, and a double-axis kneader as performed usually.

The rubber composition for tires according to the present invention maybe kneaded, if required, with compounding agents such as vulcanizingagent, vulcanizing auxiliary, anti-oxidant, filler, process oil, zincwhite, and stearic acid, as usually employed in the rubber industry.

Available examples of the vulcanizing agent include publicly knownvulcanizing agents, for example, sulfur, organic peroxide, resinousvulcanizing agent, metallic oxide such as magnesium oxide.

Available examples of the vulcanizing auxiliary include publicly knownvulcanizing auxiliaries, for example, aldehydes, ammonias, amines,guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, andxanthates.

Examples of the anti-oxidant include amine-ketone series, imidazoleseries, amine series, phenol series, sulfur series, and phosphorousseries.

Examples of the filler include inorganic fillers such as calciumcarbonate, basic magnesium carbonate, clay, litharge, and diatom earth;and organic fillers such as reclaimed rubber and powdered rubber.

Available examples of the process oil include aromatic series, naphtheneseries, and paraffin series.

The crosslinking coagent compounded in the rubber composition for golfballs according to the present invention comprises preferably amonovalent or divalent metal salt of α,β-ethylenic unsaturatedcarboxylic acid, of which specific examples include zinc diacrylate,basic zinc methacrylate, and zinc dimethacrylate. These metal salts ofα,β-ethylenic unsaturated carboxylic acid may be mixed directly with thebase material rubber in a normal method. Alternatively, into a rubbercomposition including a metal oxide such as zinc oxide previouslykneaded therein, an α,β-ethylenic unsaturated carboxylic acid such asacrylic acid and methacrylic acid is added and kneaded. This causesreaction of the α, β-ethylenic unsaturated carboxylic acid with themetal oxide in the rubber composition, resulting in the metal salt ofα,β-ethylenic unsaturated carboxylic acid.

Preferably, the compounded quantity of the crosslinking coagent is equalto 10-50 parts by weight to 100 parts by weight of the base materialrubber. A compounded quantity of the crosslinking coagent less than theabove range can not proceed crosslinking sufficiently, resulting inlowered rebound performance, shortened carry, and worsened durability.In contrast, a compounded quantity of the crosslinking coagent more thanthe above range results in excessive large compression, which worsensthe feeling of impact.

In the rubber composition for golf balls according to the presentinvention, preferably, a rubber composition contained in the gummyportion is mixed with peroxides as an essential component, in additionto the crosslinking coagent.

The peroxides act as the initiator for crosslinking, grafting andpolymerizing the rubber and the crosslinking coagent. Suitable examplesof the peroxides include dicumyl peroxide, and 1,1-bis(t-butylperoxy)3,3,5-trimethyl cyclohexane.

Preferably, the compounded quantity of the peroxides is equal to 0.2-5parts by weight to 100 parts by weight of the base material rubber. Acompounded quantity of the peroxides less than the above range can notproceed crosslinking sufficiently, resulting in lowered reboundperformance, shortened carry, and worsened durability. In contrast, acompounded quantity of the peroxides more than the above range resultsin over curing (excessive crosslinking) and accordingly crispness, whichworsens durability.

In the rubber composition for golf balls according to the presentinvention, a zinc oxide also serving as a crosslinking auxiliary may bemixed if the crosslinking coagent is zinc acrylate or zinc methacrylate.Further, a filler such as barium sulfate, an anti-oxidant, and anadditive such as zinc stearate may be mixed, if required.

EXAMPLES

The catalyst for polymerization of conjugated diene according to thepresent invention was used to produce butadiene as the conjugated dienepolymer. Examples thereof are described next with polymerizationconditions and polymerization results shown in Tables 1-7.

A microstructure was determined through the infrared absorption spectrumanalysis. The microstructure was calculated from an absorption intensityratio with Cis 740 cm⁻¹, Trans 967 cm⁻¹, Vinyl 910 cm⁻¹.

An inherent viscosity [η] was measured at 30° C. using a solution ofpolymer in toluene.

Example 1

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 2 ml of a solution of triethylaluminum (TEA) in toluene (1 mol/L) was added, followed by agitation for3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumtriisopropoxide in toluene (0.1 mol/L) was added, and heated up to 40°C. After agitation for 3 minutes, 1 ml of a solution of triphenylcarbenium tetrakis (pentafluoro phenyl) borate in toluene (0.43 mol/L)was added to initiate polymerization. After polymerization at 40° C. for30 minutes, 5 ml of a solution of ethanol/heptane (1/1) containing ananti-oxidant was added to terminate the polymerization. After thepressure inside the autoclave was released, the polymerization solutionwas supplied into ethanol to recover polybutadiene. The recoveredpolybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 1.

Example 2

Except for the solution of triethyl aluminum (TEA) in toluene (1 mol/L)added by a volume of 4 ml, polymerization was performed similar toExample 1. The polymerization result is shown in Table 1.

Example 3

Except for the solution of triethyl aluminum (TEA) in toluene (5 mol/L)added by a volume of 1.2 ml, polymerization was performed similar toExample 1. The polymerization result is shown in Table 1.

Comparative Example 1

Except for the use of tris(pentafluoro phenyl) borane instead oftriphenyl carbenium tetrakis(pentafluoro phenyl) borate, polymerizationwas performed similar to Example 3. Any polymer could not be produced atall.

Example 4

Except for the solution of triethyl aluminum (TEA) in toluene (5 mol/L)added by a volume of 2.4 ml, polymerization was performed similar toExample 1. The polymerization result is shown in Table 1.

Comparative Example 2

Except for the use of methyl alumoxane instead of triethyl aluminum(TEA) and without the use of triphenyl carbenium tetrakis(pentafluorophenyl) borate, polymerization was performed similar to Example 4. Anypolymer could not be produced at all.

Example 5

Except for the solution of yttrium triisopropoxide in toluene (0.1mol/L) added by a volume of 0.8 ml, polymerization was performed similarto Example 2. The polymerization result is shown in Table 1.

Example 6

Except for the solution of triethyl aluminum (TEA) in toluene (2 mol/L)added by a volume of 3.2 ml, polymerization was performed similar toExample 5. The polymerization result is shown in Table 1.

Example 7

Except for the solution of triethyl aluminum (TEA) in toluene (2 mol/L)added by a volume of 4.8 ml, polymerization was performed similar toExample 5. The polymerization result is shown in Table 1.

TABLE 1 Activity gPB/ Y(OiPr)3 [Al] mmol- Microstructure (%) mM Al mM Y· h Cis Trans Vinyl [η] Ex- ample No 1 0.5 TEA 5 112 97.8 1.5 0.7 4.9 20.5 TEA 10 309 95.2 3.8 1.0 1.7 3 0.5 TEA 15 395 93.9 4.9 1.2 1.4 4 0.5TEA 30 358 89.2 9.5 1.3 1.0 5 0.2 TEA 10 287 94.9 4.2 0.9 1.9 6 0.2 TEA16 438 92.0 6.9 1.1 1.3 7 0.2 TEA 24 450 89.9 8.8 1.3 1.1 Com- parativeEx- ample 1 0.5 TEA 15 0 — — — — 2 0.5 MMAO 30 0 — — — —

Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), B/Y=2, Polymerization Temperature        40° C., Polymerization Time 30 min.

Adding Order:

-   -   Toluene-Bd-30° C.-TEA-3 min-Y-40° C.-B

Example 8

Except for the agitation time determined 10 minutes after addition ofthe solution of yttrium triisopropoxide in toluene, polymerization wasperformed similar to Example 1. The polymerization result is shown inTable 2.

Example 9

Except for the agitation time determined 20 minutes after addition ofthe solution of yttrium triisopropoxide in toluene, polymerization wasperformed similar to Example 1. The polymerization result is shown inTable 2.

Example 10

Except for the agitation time determined 30 minutes after addition ofthe solution of yttrium triisopropoxide in toluene, polymerization wasperformed similar to Example 1. The polymerization result is shown inTable 2.

TABLE 2 Mature Activity Example Time Yield gPB/mmol- Microstructure (%)No min g/l Y · h Cis Trans Vinyl [η] 1 3 28.0 112 97.8 1.5 0.7 4.9 8 1052.8 211 97.3 1.9 0.8 3.7 9 20 66.4 266 96.9 2.3 0.8 3.4 10 30 67.8 27197.0 2.2 0.8 3.5

Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C., Polymerization Time 30 min, Y(OiPr)₃ 0.5 mM,        TEA 5 mM

Adding Order:

-   -   Toluene-Bd-30° C.-TEA-3 min-Y-(Time Variation)-40° C.-Borate

Example 11

Except for the use of diethyl aluminum hydride (DEAH) instead oftriethyl aluminum (TEA), polymerization was performed similar toExample 1. The polymerization result is shown in Table 3.

Example 12

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by a volume of 3 ml, polymerization was performed similarto Example 11. The polymerization result is shown in Table 3.

Example 13

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by a volume of 4 ml, polymerization was performed similarto Example 1. The polymerization result is shown in Table 3.

Example 14

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by a volume of 6 ml, polymerization was performed similarto Example 1. The polymerization result is shown in Table 3.

TABLE 3 Activity Exam- gPB/ ple Y(OiPr)3 DEAH Yield mmol- Microstructure(%) No mM mM g/l Y · h Cis Trans Vinyl [η] 11 0.5 5.0 97.1 388 97.3 1.90.8 2.9 12 0.5 7.5 55.7 223 97.1 1.9 1.0 1.7 13 0.5 10.0 39.5 158 98.31.0 0.7 1.4 14 0.5 15.0 80.0 320 98.4 0.9 0.7 1.1

Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C., Polymerization Time 30 min.

Adding Order:

-   -   Toluene-Bd-30° C.-DEAH-3 min-Y-40° C.-Borate

Example 15

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 2 ml of a solution of triethylaluminum (TEA) in toluene (1 mol/L) was added, followed by agitation for3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumtriisopropoxide in toluene (0.1 mol/L) was added, and heated up to 40°C. After agitation for 3 minutes, 1 ml of a solution of triphenylcarbenium tetrakis (pentafluoro phenyl) borate in toluene (0.43 mol/L),and 0.4 ml of a solution of dibutyl magnesium in heptane (1 mol/L) wereadded to initiate polymerization. After polymerization at 40° C. for 30minutes, 5 ml of a solution of ethanol/heptane (1/1) containing ananti-oxidant was added to terminate the polymerization. After thepressure inside the autoclave was released, the polymerization solutionwas supplied into ethanol to recover polybutadiene. The recoveredpolybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 4.

Example 16

Except for the solution of dibutyl magnesium in heptane (1 mol/L) addedby a volume of 0.8 ml, polymerization was performed similar to Example15. The polymerization activity was extremely high and thepolymerization was terminated after 25 minutes. The polymerizationresult is shown in Table 4.

Example 17

Except for the solution of dibutyl magnesium in heptane (1 mol/L) addedby a volume of 2 ml, polymerization was performed similar to Example 15.The polymerization result is shown in Table 4.

Example 18

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 0.8 ml of a solution oftriethyl aluminum (TEA) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 0.8 ml of a solution ofyttrium triisopropoxide in toluene (0.1 mol/L) was added, and heated upto 40° C. After agitation for 3 minutes, 0.4 ml of a solution oftriphenyl carbenium tetrakis (pentafluoro phenyl) borate in toluene(0.43 mol/L), and 0.16 ml of a solution of dibutyl magnesium in heptane(1 mol/L) were added to initiate polymerization. After polymerization at40° C. for 30 minutes, 5 ml of a solution of ethanol/heptane (1/1)containing an anti-oxidant was added to terminate the polymerization.After the pressure inside the autoclave was released, the polymerizationsolution was supplied into ethanol to recover polybutadiene. Therecovered polybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 4.

Example 19

Except for the solution of dibutyl magnesium in heptane (1 mol/L) addedby a volume of 0.32 ml, polymerization was performed similar to Example18. The polymerization activity was extremely high and thepolymerization was terminated after 21 minutes. The polymerizationresult is shown in Table 4.

Example 20

Except for the solution of dibutyl magnesium in heptane (1 mol/L) addedby a volume of 0.8 ml, polymerization was performed similar to Example18. The polymerization result is shown in Table 4.

Example 21

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 0.4 ml of a solution oftriethyl aluminum (TEA) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 0.4 ml of a solution ofyttrium triisopropoxide in toluene (0.1 mol/L) was added, and heated upto 40° C. After agitation for 3 minutes, 0.2 ml of a solution oftriphenyl carbenium tetrakis (pentafluoro phenyl) borate in toluene(0.43 mol/L), and 0.16 ml of a solution of dibutyl magnesium in heptane(1 mol/L) were added to initiate polymerization. After polymerization at40° C. for 30 minutes, 5 ml of a solution of ethanol/heptane (1/1)containing an anti-oxidant was added to terminate the polymerization.After the pressure inside the autoclave was released, the polymerizationsolution was supplied into ethanol to recover polybutadiene. Therecovered polybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 4.

Example 22

Except for the solution of triethyl aluminum (TEA) in heptane (1 mol/L)added by a volume of 0.8 ml, polymerization was performed similar toExample 21. The polymerization result is shown in Table 4.

Example 23

Except for the solution of triethyl aluminum (TEA) in heptane (1 mol/L)added by a volume of 2 ml, polymerization was performed similar toExample 21. The polymerization result is shown in Table 4.

TABLE 4 Poly Activity Example Y(OiPr)3 TEA Bu₂Mg Time Yield gPB/Microstructure (%) No mM mM mM min g/l mmol-Y · h Cis Trans Vinyl [η] 150.5 5.0 1.0 30 89 355 93.0 5.6 1.4 0.9 16 0.5 5.0 2.0 25 184 885 91.37.6 1.1 1.6 17 0.5 5.0 5.0 30 48 191 86.0 12.2 1.8 0.4 18 0.2 2.0 0.4 307 67 95.1 3.7 1.2 0.9 19 0.2 2.0 0.8 21 140 2000 95.9 3.2 0.9 2.7 20 0.22.0 2.0 30 41 410 93.0 5.6 1.4 0.7 21 0.1 1.0 0.4 30 93 1860 97.0 2.10.9 4.0 22 0.1 2.0 0.4 30 96 1930 96.2 2.9 0.9 2.9 23 0.1 5.0 0.4 30 29590 95.2 3.7 1.1 1.2

Poly Time: Polymerization Time Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C.

Adding Order:

-   -   Toluene−Bd-30° C.-TEA-3 min-Y-40° C.-Borate-Bu₂Mg

Example 24

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then a hydrogen gas is supplied at apartial pressure of 1.0 Kg/cm², and 2 ml of a solution of triethylaluminum (TEA) in toluene (1 mol/L) was added, followed by agitation for3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumtriisopropoxide in toluene (0.1 mol/L) was added, and heated up to 40°C. After agitation for 3 minutes, 1 ml of a solution of triphenylcarbenium tetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L)was added to initiate polymerization. After polymerization at 40° C. for30 minutes, 5 ml of a solution of ethanol/heptane (1/1) containing ananti-oxidant was added to terminate the polymerization. After thepressure inside the autoclave was released, the polymerization solutionwas supplied into ethanol to recover polybutadiene. The recoveredpolybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 5.

Example 25

Except for the partial pressure of the hydrogen gas supplied at 2.75Kg/cm², polymerization was performed similar to Example 24. Thepolymerization result is shown in Table 5.

TABLE 5 H₂ Activity Partial gPB/ Run Y(OiPr)₃ Pressure Yield mmol-Microstructure (%) No mM kgf/cm² g/l Y · h Cis Trans Vinyl [η] 1 0.5 034.2 112 97.8 1.5 0.7 4.9 24 0.5 1.0 31.5 126 97.6 1.6 0.8 3.5 25 0.52.75 30.5 122 97.8 1.6 0.6 3.0

Polymerization Conditions:

-   -   Toluene FB=400 ml (Bd 140 ml), Y(OiPr)₃ 0.5 mM, Al/Y=10, B/Y=2,        40° C.×30 min.

Adding Order:

-   -   Toluene-Bd-H₂-30° C.-TEA-3 min-Y-40° C.-Borate

Example 26

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 2.5 ml of a slurry of lithiumaluminum hydride in toluene (30 g/L), and 2 ml of a solution of triethylaluminum (TEA) in toluene (1 mol/L) were added, followed by agitationfor 3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumtriisopropoxide in toluene (0.1 mol/L) was added, and heated up to 40°C. After agitation for 3 minutes, 1 ml of a solution of triphenylcarbenium tetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L)was added to initiate polymerization. After polymerization at 40° C. for30 minutes, 5 ml of a solution of ethanol/heptane (1/1) containing ananti-oxidant was added to terminate the polymerization. After thepressure inside the autoclave was released, the polymerization solutionwas supplied into ethanol to recover polybutadiene. The recoveredpolybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 6.

Example 27

Except for the slurry of lithium aluminum hydride in toluene added by 5ml, polymerization was performed similar to Example 26. Thepolymerization result is shown in Table 6.

TABLE 6 Activity gPB/ Run TEA LiAlH₄ Yield mmol- Microstructure (%) NomM mM Al/y g/l Y · h Cis Trans Vinyl [η] 1 5.0 0 10 34.2 112 97.8 1.50.7 4.9 26 5.0 5 20 35.0 175 96.7 2.4 0.9 3.4 27 5.0 10 30 47.5 238 95.73.2 1.1 2.5

Polymerization Conditions:

-   -   Toluene FB=400 ml (Bd 140 ml), Y(OiPr)₃ 0.5 mM, Borate/Y=2, 40°        C.×30 min.

Adding Order:

-   -   Toluene FB-30° C.-TEA-LiAlH4-3 min-Y-40° C.-Borate

Example 28

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 2 ml of a solution of diethylaluminum hydride (DEAH) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumoctylate in toluene (0.1 mol/L) was added, and heated up to 40° C. Afteragitation for 3 minutes, 1 ml of a solution of triphenyl carbeniumtetrakis (pentafluoro phenyl) borate in toluene (0.43 mol/L) was addedto initiate polymerization. After polymerization at 40° C. for 25minutes, 5 ml of a solution of ethanol/heptane (1/1) containing ananti-oxidant was added to terminate the polymerization. After thepressure inside the autoclave was released, the polymerization solutionwas supplied into ethanol to recover polybutadiene. The recoveredpolybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 7. Because of an excessive highmolecular weight, the microstructure and inherent viscosity can not bemeasured.

Example 29

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 3 ml, and the polymerization time determined 30 minutes,polymerization was performed similar to Example 28. The polymerizationresult is shown in Table 7.

Example 30

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 4 ml, polymerization was performed similar to Example25. The polymerization result is shown in Table 7.

Example 31

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (2mol/L) added by 3 ml, polymerization was performed similar to Example25. The polymerization result is shown in Table 7.

Example 32

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (2mol/L) added by 5 ml, polymerization was performed similar to Example25. The polymerization result is shown in Table 7.

TABLE 7 Poly Activity Y(Oct)3 DEAH Time Yield gPB/mmol- Microstructure(%) Example No mM mM min g/l Y · h Cis Trans Vinyl [η] 28 0.5 5.0 2545.1 216 — — — — 29 0.5 7.5 30 38.8 155 99.0 0.4 0.6 4.5 30 0.5 10.0 3041.0 164 98.5 0.9 0.6 2.2 31 0.5 15.0 30 60.8 243 98.6 0.7 0.7 1.3 320.5 25.0 30 83.7 335 98.2 1.1 0.7 0.9

Poly Time: Polymerization Time Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C.

Adding Order:

-   -   Toluene-Bd-30° C.-DEAH-3 min-Y-40° C.-Borate

Example 33

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 2 ml of a solution of triethylaluminum (TEA) in toluene (1 mol/L) was added, followed by agitation for3 minutes at 500 rpm. Next, 1 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (40mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 0.2 ml of a solution of triphenyl carbeniumtetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L) was added toinitiate polymerization. After polymerization at 40° C. for 20 minutes,5 ml of a solution of ethanol/heptane (1/1) containing an anti-oxidantwas added to terminate the polymerization. After the pressure inside theautoclave was released, the polymerization solution was supplied intoethanol to recover polybutadiene. The recovered polybutadiene was driedin vacuum at 70° C. for 6 hours. The polymerization result is shown inTable 8.

Example 34

Except for the solution of triethyl aluminum (TEA) in toluene (5 mol/L)added by 1.2 ml, and the polymerization time determined 30 minutes,polymerization was performed similar to Example 1. The polymerizationresult is shown in Table 8.

Example 35

Except for the solution of tris(2,2,6,6-tetramethyl heptane-3,5-dionate)yttrium in toluene (40 mmol/L) added by 0.5 ml, the solution oftriphenyl carbenium tetrakis (pentafluoro phenyl) borate in toluene(0.43 mol/L) added by 0.1 ml, the solution of triethyl aluminum (TEA) intoluene (1 mol/L) added by 1 ml, and the polymerization time determined30 minutes, polymerization was performed similar to Example 1. Thepolymerization result is shown in Table 8.

Example 36

Except for the solution of triethyl aluminum (TEA) in toluene (1 mol/L)added by 2 ml, polymerization was performed similar to Example 3. Thepolymerization result is shown in Table 8.

Example 37

Except for the solution of triethyl aluminum (TEA) in toluene (2 mol/L)added by 2 ml, polymerization was performed similar to Example 3. Thepolymerization result is shown in Table 8.

TABLE 8 Activity Example Y(tmhd)3 TEA Poly Time Yield gPB/mmol-Microstructure (%) No mM mM min g/l Y · h Cis Trans Vinyl [η] 33 0.1 5.020 108.8 3,260 94.7 4.3 1.0 3.7 34 0.1 15.0 30 103.5 2,070 92.5 6.5 1.02.1 35 0.05 2.5 30 71.9 2,880 95.8 3.2 1.0 3.9 36 0.05 5.0 30 104.44,170 94.7 4.3 1.0 3.3 37 0.05 10.0 30 65.3 2,610 94.6 4.4 1.0 2.2

Poly Time: Polymerization Time Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), B/Y=2, Polymerization Temperature        40° C., Polymerization Time 30 min

Adding Order:

-   -   Toluene-Bd-30° C.-TEA-3 min-Y-40° C.-B

Example 38

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 2 ml of a solution of diethylaluminum hydride (DEAH) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 2 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (40mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 0.4 ml of a solution of triphenyl carbeniumtetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L) was added toinitiate polymerization. After polymerization at 40° C. for 30 minutes,5 ml of a solution of ethanol/heptane (1/1) containing an anti-oxidantwas added to terminate the polymerization. After the pressure inside theautoclave was released, the polymerization solution was supplied intoethanol to recover polybutadiene. The recovered polybutadiene was driedin vacuum at 70° C. for 6 hours. The polymerization result is shown inTable 9.

Example 39

Except for the solution of tris(2,2,6,6-tetramethyl heptane-3,5-dionate)yttrium in toluene (40 mmol/L) added by 1 ml, the solution of triphenylcarbenium tetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L)added by 0.2 ml, and the solution of diethyl aluminum hydride (DEAH) intoluene (1 mol/L) added by 0.5 ml, polymerization was performed similarto Example 38. The polymerization result is shown in Table 9.

Example 40

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 1 ml, polymerization was performed similar to Example39. The polymerization result is shown in Table 9.

Example 41

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 2 ml, polymerization was performed similar to Example39. The polymerization result is shown in Table 9.

Example 42

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 3.2 ml, polymerization was performed similar to Example39. The polymerization result is shown in Table 9.

TABLE 9 Poly Activity Example Y(tmhd)3 DEAH Time Yield gPB/mmol-Microstructure (%) No mM mM min g/l Y · h Cis Trans Vinyl [η] 38 0.2 5.030 125.1 1,250 98.8 0.7 0.5 2.9 39 0.1 1.3 30 66.7 1,330 98.5 0.8 0.76.8 40 0.1 2.5 30 64.5 1,290 98.6 0.7 0.7 3.6 41 0.1 5.0 30 122.4 2,45098.4 1.0 0.6 2.3 42 0.1 8.0 30 128.2 2,560 98.3 1.1 0.6 1.8

Poly Time: Polymerization Time Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), B/Y=2, Polymerization Temperature        40° C., Polymerization Time 30 min

Adding Order:

-   -   Toluene-Bd-30° C.-TEA-3 min-Y-40° C.-B

Example 43

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 3 ml of a solution of triethylaluminum (TEA) in toluene (1 mol/L) was added, followed by agitation for3 minutes at 500 rpm. Next, 1 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (20mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 0.1 ml of a solution of triphenyl carbeniumtetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L) was added toinitiate polymerization. After polymerization at 40° C. for 30 minutes,5 ml of a solution of ethanol/heptane (1/1) containing an anti-oxidantwas added to terminate the polymerization. After the pressure inside theautoclave was released, the polymerization solution was supplied intoethanol to recover polybutadiene. The recovered polybutadiene was driedin vacuum at 70° C. for 6 hours. The polymerization result is shown inTables 10 and 11.

Example 44

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 0.7 ml of a solution of diethylaluminum hydride (DEAH) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 1 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (20mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 0.1 ml of a solution of triphenyl carbenium tetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L) was added toinitiate polymerization. After polymerization at 40° C. for 30 minutes,5 ml of a solution of ethanol/heptane (1/1) containing an anti-oxidantwas added to terminate the polymerization. After the pressure inside theautoclave was released, the polymerization solution was supplied intoethanol to recover polybutadiene. The recovered polybutadiene was driedin vacuum at 70° C. for 6 hours. The polymerization result is shown inTable 10.

Example 45

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml ofcyclohexane and 140 ml of butadiene was brought therein. The temperatureof the solution was elevated up to 30° C., then 2 ml of a solution oftriethyl aluminum (TEA) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 1 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (20mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 10 ml of a solution of triphenyl carbenium tetrakis(pentafluorophenyl) borate in toluene (4 mmol/L) was added to initiatepolymerization. After polymerization at 40° C. for 30 minutes, 5 ml of asolution of ethanol/heptane (1/1) containing an anti-oxidant was addedto terminate the polymerization. After the pressure inside the autoclavewas released, the polymerization solution was supplied into ethanol torecover polybutadiene. The recovered polybutadiene was dried in vacuumat 70° C. for 6 hours. The polymerization result is shown in Table 10.

Example 46

Except for the solution of triethyl aluminum (TEA) in toluene (1 mol/L)added by 3 ml, polymerization was performed similar to Example 45. Thepolymerization result is shown in Table 10.

Example 47

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml ofcyclohexane and 140 ml of butadiene was brought therein. The temperatureof the solution was elevated up to 30° C., then 0.7 ml of a solution ofdiethyl aluminum hydride (DEAH) in toluene (1 mol/L) was added, followedby agitation for 3 minutes at 500 rpm. Next, 1 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (20mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 10 ml of a solution of triphenyl carbenium tetrakis(pentafluoro phenyl) borate in toluene (4 mmol/L) was added to initiatepolymerization. After polymerization at 40° C. for 30 minutes, 5 ml of asolution of ethanol/heptane (1/1) containing an anti-oxidant was addedto terminate the polymerization. After the pressure inside the autoclavewas released, the polymerization solution was supplied into ethanol torecover polybutadiene. The recovered polybutadiene was dried in vacuumat 70° C. for 6 hours. The polymerization result is shown in Table 10.

Example 48

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 0.06 ml of a solution of carbondisulfide (CS₂) in toluene (0.2 mol/L), and 3 ml of a solution oftriethyl aluminum (TEA) in toluene (1 mol/L) were added, followed byagitation for 3 minutes at 500 rpm. Next, 1 ml of a solution oftris(2,2,6,6-tetramethyl heptane-3,5-dionato) yttrium in toluene (20mmol/L) was added, and heated up to 40° C. After agitation for 4minutes, 0.1 ml of a solution of triphenyl carbenium tetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L) was added toinitiate polymerization. After polymerization at 40° C. for 30 minutes,5 ml of a solution of ethanol/heptane (1/1) containing an anti-oxidantwas added to terminate the polymerization. After the pressure inside theautoclave was released, the polymerization solution was supplied intoethanol to recover polybutadiene. The recovered polybutadiene was driedin vacuum at 70° C. for 6 hours. The polymerization result is shown inTable 11.

Example 49

Except for the solution of carbon disulfide (CS₂) in toluene (0.2 mol/L)added by 0.12 ml, polymerization was performed similar to Example 48.The polymerization result is shown in Table 11.

Example 50

Except for the solution of carbon disulfide (CS₂) in toluene (0.2 mol/L)added by 0.24 ml, polymerization was performed similar to Example 48.The polymerization result is shown in Table 11.

TABLE 10 Solvent: Cyclohexane Activity Example Al Yield gPB/mmol-Microstructure (%) No Solvent mM g/l Y · h Cis Trans Vinyl [η] 43Toluene TEA 7.5 83.1 3,320 94.8 4.1 1.1 2.6 44 Toluene DEAH 1.8 53.22,130 97.5 1.5 1.0 2.7 45 Cyclohexane TEA 5.0 9.5 380 90.5 7.8 1.7 1.846 Cyclohexane TEA 7.5 26.4 1,050 90.2 8.1 1.7 1.9 47 Cyclohexane DEAH1.8 15.0 600 92.7 4.3 3.0 0.7

Polymerization Conditions:

-   -   Solvent+Bd=400 ml (Bd 140 ml), Y(tmhd)₃ 0.05 mM, B/Y=2,        Polymerization Temperature 40° C., Polymerization Time 30 min

Adding Order:

-   -   Solvent-Bd-30° C.-Al-3 min-Y-40° C.-B

TABLE 11 Example CS₂ Yield Activity Microstructure (%) No mM g/lgPB/mmol-Y · h Cis Trans Vinyl [η] 43 0 83.1 3,320 94.8 4.1 1.1 2.6 480.03 53.7 2,150 95.9 3.2 0.9 2.8 49 0.06 43.1 1,720 96.9 2.3 0.8 3.3 500.12 29.2 1,170 97.0 2.1 0.9 3.3

Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Y(tmbd)3 0.05 mM, TEA 7.5 mM,        B/Y=2, Polymerization Temperature 40° C., Polymerization Time 30        min

Adding Order:

-   -   Toluene-Bd-CS₂-30° C.-Al-3 min-Y-40° C.-B

Except for the use of a neodecanoate (Nd(Ver)₃) instead oftris(2,2,6,6-tetramethyl heptane-3,5-dionate) yttrium, polymerization inComparative Examples 3 and 4 were performed similar to Examples 36 and41. The results are shown in Table 12. As can be seen from Table 12, theactivity on polymerization is higher when the tris(2,2,6,6-tetramethylheptane-3,5-dionate) yttrium is used than when the neodymiumneodecanoate is used.

TABLE 12 Activity Catalyst Al Al/Y Yield gPB/mmol- Microstructure Run mMmM mol/mol g/l Y · h Cis Trans Vinyl [η] No E36 Y(tmhd)₃ 0.05 TEA 5.0100 104.4 4,170 94.7 4.3 1.0 3.3 171 E41 0.1 DEAH 5.0 50 122.4 2,45098.4 1.0 0.6 2.3 179 C3 Nd(Ver)₃ 0.05 TEA 5.0 100 14.5 580 97.5 1.3 1.23.1 YS-362 C4 0.1 DEAH 5.0 50 37.5 750 97.5 1.3 1.2 1.0 363

E36: Example 36, E41: Example 41 C3: Comparative Example 3, C4:Comparative Example 4 Polymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C., Polymerization Time 30 min

Adding Order:

-   -   Toluene-Bd-30° C.-Al-3 min-Nd-40° C.-Borate

Next, examples of the rubber composition for tires according to thepresent invention will be specifically described. A microstructure wasdetermined through the infrared absorption spectrum analysis and aninherent viscosity was measured similarly.

A molecular weight (Mw, Mn) was measured with a GPC method: HLC-8220(available from Toso Inc.) and calculated by the standard polystyreneconversion.

A Mooney viscosity (ML₁₊₄, 100° C.) was measured on the basis of JIS6300.

Die swell; obtained as an index of extrusion processability of thecompounded product, using a processability tester (MPT: available fromMonsanto Inc.), by measuring a ratio of a sectional area of thecompounded product on extrusion at 100° C. and a shearing speed of 100sec⁻¹ to a die orifice sectional area (where L/D=1.5 mm/1.5 mm).

Lambourn abrasion was measured at a slip rate of 20% in accordance witha measuring method stipulated under JIS-K6264 and indicated with anindex based on 100 of Comparative Example 1 (the larger the index, thebetter).

A flex crack-growth test was performed in accordance with a measuringmethod stipulated under JIS K6260. A crack length was measured after50,000 times of flexing at a stroke of 30 mm and indicated with an indexbased on 100 of Comparative Example 1 (the larger the index, thebetter).

The quantity of heat radiation/permanent distortion; measured on thebasis of a measuring method stipulated under JIS K6265.

Polymerization Example 1

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 3 ml of a solution of diethylaluminum hydride (DEAH) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumoctylate in toluene (0.1 mol/L) was added, and heated up to 40° C. Afteragitation for 3 minutes, 1 ml of a solution of triphenyl carbeniumtetrakis (pentafluoro phenyl) borate in toluene (0.43 mol/L) was addedto initiate polymerization. After polymerization at 40° C. for 30minutes, 5 ml of a solution of ethanol/heptane (1/1) containing ananti-oxidant was added to terminate the polymerization. After thepressure inside the autoclave was released, the polymerization solutionwas supplied into ethanol to recover polybutadiene. The recoveredpolybutadiene was dried in vacuum at 70° C. for 6 hours. Thepolymerization result is shown in Table 13.

Polymerization Example 2

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 4 ml, polymerization was performed similar toPolymerization Example 1. The polymerization result is shown in Table13.

Polymerization Example 3

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (2mol/L) added by 3 ml, polymerization was performed similar toPolymerization Example 1. The polymerization result is shown in Table13.

Polymerization Example 4

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (2mol/L) added by 5 ml, polymerization was performed similar toPolymerization Example 1. The polymerization result is shown in Table13.

Polymerization Example 5

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 1.9 ml, and the solution of tris(2,2,6,6-tetramethylheptane-3,5-dionate) yttrium in toluene (0.1 mol/L) added by 0.8 mlinstead of yttrium octylate, polymerization was performed similar toPolymerization Example 1. The polymerization result is shown in Table13.

TABLE 13 Activity Poly Y(Oct)3 DEAH Poly Time Yield gPB/mmol-Microstructure (%) Exam No mM mM min g/l Y· h Cis Trans Vinyl [η] 1 0.57.5 30 38.8 155 99.0 0.4 0.6 4.5 2 0.5 10.0 30 41.0 164 98.5 0.9 0.6 2.23 0.5 15.0 30 60.8 243 98.6 0.7 0.7 1.3 4 0.5 25.0 30 83.7 335 98.2 1.10.7 0.9 Y(tBuAA)3 5 0.2 4.8 30 53.3 533 98.4 0.9 0.7 2.5

Poly Exam: Polymerization Example Poly Time Polymerization TimePolymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C.

Adding Order:

-   -   Toluene-Bd-30° C.-DEAH-3 min-Y-40° C.-Borate

Examples 51-53

In accordance with a compounding table in Table 14, primary compoundingwas implemented with the use of a Plast Mill to mix the BR ofPolymerization Example 5, natural rubber, carbon black, process oil,zinc white, a stearic acid, and an anti-oxidant together. Then,secondary compounding was implemented with the use of a roll to add avulcanization promoter, and sulfur therein to produce a compoundedrubber. This compounded rubber was used to measure the Mooney viscosityand the die swell. Further, the compounded rubber was molded inaccordance with the aimed physical property and press-vulcanized at 150°C. to produce a vulcanized product, which was then subjected tomeasurement of the physical property.

The extruded product has excellent dimensional stability and niceabrasion resistance and flex crack-growth endurance as well as greatlyimproved heat radiation characteristics (the quantity of heat radiation,and the permanent distortion).

Comparative Examples 5, 6

Except for the use of BR150, BR150L (high-cis polybutadiene rubbersavailable from Ube Industries, Ltd.) instead of the BR of PolymerizationExample 5, compounding was performed similar to Examples 51-53.

TABLE 14 Comparative Example Example 51 52 53 5 6 Polymerization 50 7030 Example 6 BR150 50 BR150L 50 NR(RSS#1) 50 50 50 50 50 CompoundedProduct 85 83 87 78 85 ML Die Swell 2.16 2.12 2.18 2.31 2.20 LambornAbrasion 101 103 100 100 102 Flex Crack Growth 108 106 115 100 105 HeatRadiation Test Heat Radiation (° C.) 27 28 25 34 32 Permanent Distortion(%) 8 9 7 13 11 *Other Compounding Agents Carbon black 50 MitsubishiChemical Diablack I Process oil 3 Esso Oil 110 Zinc oxide 3

Next, examples of the rubber composition for golf balls according to thepresent invention will be specifically described. The polymerizationconditions and polymerization results are described together on Table15. The microstructure was determined through the infrared absorptionspectrum analysis, and the inherent viscosity ([η]) and the Mooneyviscosity (ML₁₊₄, 100° C.) of the raw rubber and the compounded productwere measured similarly.

Roll processability was determined by visually observing the windingstate of the compounded product wound around a 6-inch roll at 50° C.

Hardness was measured in accordance with a measuring method stipulatedunder JIS-K6253 using a durometer (type D).

Tensile strength was measured in accordance with a measuring methodstipulated under JIS-K6251 using a No. 3 dumbbell at a tensile rate of500 mm/min.

Rebound resilience was measured in accordance with a measuring methodstipulated under JIS-K6251 in a tripso-impact resilience test.

Example 54

An autoclave with an inner volume of 2 L was provided. The insidethereof was substituted by nitrogen, and a solution of 260 ml of tolueneand 140 ml of butadiene was brought therein. The temperature of thesolution was elevated up to 30° C., then 3 ml of a solution of diethylaluminum hydride (DEAH) in toluene (1 mol/L) was added, followed byagitation for 3 minutes at 500 rpm. Next, 2 ml of a solution of yttriumoctylate in toluene (0.1 mol/L) was added, and heated up to 40° C. Afteragitation for 3 minutes, 1 ml of a solution of triphenyl carbeniumtetrakis(pentafluoro phenyl) borate in toluene (0.43 mol/L) was added toinitiate polymerization. After polymerization at 40° C. for 30 minutes,5 ml of a solution of ethanol/heptane (1/1) containing an anti-oxidantwas added to terminate the polymerization. After the pressure inside theautoclave was released, the polymerization solution was supplied intoethanol to recover polybutadiene. The recovered polybutadiene was driedin vacuum at 70° C. for 6 hours. The polymerization result is shown inTable 15.

Example 55

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (1mol/L) added by 4 ml, polymerization was performed similar to Example54. The polymerization result is shown in Table 15.

Example 56

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (2mol/L) added by 3 ml, polymerization was performed similar to Example54. The polymerization result is shown in Table 15.

Example 57

Except for the solution of diethyl aluminum hydride (DEAH) in toluene (2mol/L) added by 5 ml, polymerization was performed similar to Example54. The polymerization result is shown in Table 15.

TABLE 15 Activity Poly Y(Oct)3 DEAH Poly Time Yield gPB/mmol-Microstructure (%) Exam No mM mM min g/l Y · h Cis Trans Vinyl [η] 540.5 7.5 30 38.8 155 99.0 0.4 0.6 4.5 55 0.5 10.0 30 41.0 164 98.5 0.90.6 2.2 56 0.5 15.0 30 60.8 243 98.6 0.7 0.7 1.3 57 0.5 25.0 30 83.7 33598.2 1.1 0.7 0.9

Poly Exam: Polymerization Example Poly Time Polymerization TimePolymerization Conditions:

-   -   Toluene+Bd=400 ml (Bd 140 ml), Borate/Y=2, Polymerization        Temperature 40° C.

Adding Order:

-   -   Toluene-Bd-30° C.-DEAH-3 min-Y-40° C.-Borate

1-15. (canceled)
 16. A catalyst for polymerization of conjugated diene,comprising: (A) an yttrium compound; (B) an ionic compound including anon-coordinate anion and a cation; and (C) an organometallic compoundincluding an element selected from the groups 2, 12 and 13 of theperiodic table.
 17. The catalyst for polymerization of conjugated dieneaccording to claim 16, wherein the (A) yttrium compound comprises anyttrium compound having a bulky ligand in the following general formula:

where R₁, R₂, R₃ denote hydrogen or a substituent having 1-12 carbonatoms; O denotes an oxygen atom; and Y denotes an yttrium atom.
 18. Thecatalyst for polymerization of conjugated diene according to claim 16,wherein the (A) yttrium compound comprises a carboxylate.
 19. Thecatalyst for polymerization of conjugated diene according to claim 16,wherein the conjugated diene polymers include a cis-1,4-polybutadienehaving 90% or more of a cis-1,4 structure.
 20. A method of manufacturingconjugated diene polymers, comprising polymerizing a conjugated dieneusing the catalyst for polymerization according to claim
 16. 21. Themethod of manufacturing conjugated diene polymers according to claim 20,wherein the (A) yttrium compound comprises an yttrium compound having ahigh volume ligand in the following general formula:

where R₁, R₂, R₃ denote hydrogen or a substituent having 1-12 carbonatoms; O denotes an oxygen atom; and Y denotes an yttrium atom.
 22. Themethod of manufacturing conjugated diene polymers according to claim 20,wherein the step of polymerizing the conjugated diene polymer includesadjusting a molecular weight by a compound selected from (1) hydrogen,(2) a hydrogenated metallic compound and (3) a hydrogenatedorganometallic compound.
 23. The method of manufacturing conjugateddiene polymers according to claim 22, wherein the hydrogenatedorganometallic compound comprises a dialkyl aluminum hydride.
 24. Arubber composition for tires, comprising: (a) 10-90% by weight of ahigh-cis polybutadiene derived from polymerization of 1,3-butadiene inthe presence of a catalyst comprising (A) an yttrium compound, (B) anionic compound including a non-coordinate anion and a cation, and (C) anorganometallic compound including an element selected from the groups 2,12, 13 of the periodic table; (b) 90-10% by weight of a diene-basedrubber other than the (a) high-cis polybutadiene; and (c) 1-100 parts byweight of a rubber reinforcer mixed in 100 parts by weight of a rubbercomponent (a)+(b).
 25. The rubber composition for tires according toclaim 24, wherein the (A) yttrium compound comprises an yttrium compoundhaving a high volume ligand in the following general formula:

where R₁, R₂, R₃ denote hydrogen or a substituent having 1-12 carbonatoms; O denotes an oxygen atom; and Y denotes an yttrium atom.
 26. Therubber composition for tires according to claim 24, wherein the high-cispolybutadiene has a molecular weight adjusted by a compound selectedfrom (1) hydrogen, (2) a hydrogenated metallic compound and (3) ahydrogenated organometallic compound.
 27. The rubber composition fortires according to claim 26, wherein the hydrogenated organometalliccompound comprises a dialkyl aluminum hydride.
 28. The rubbercomposition for tires according to claim 24, wherein the high-cispolybutadiene comprises a cis-1,4-polybutadiene having 90% or more of acis-1,4 structure.
 29. A rubber composition for golf balls, comprising:a base polymer including a high-cis polybutadiene derived frompolymerization of 1,3-butadiene in the presence of a catalyst comprising(A) an yttrium compound, (B) an ionic compound including anon-coordinate anion and a cation, and (C) an organometallic compoundincluding an element selected from the groups 2, 12, 13 of the periodictable; and 10-50 parts by weight of a crosslinking coagent mixed in 100parts by weight of the base polymer.
 30. The rubber composition for golfballs according to claim 29, wherein the (A) yttrium compound comprisesan yttrium compound having a high volume ligand in the following generalformula:

where R₁, R₂, R₃ denote hydrogen or a substituent having 1-12 carbonatoms; O denotes an oxygen atom; and Y denotes an yttrium atom.
 31. Therubber composition for golf balls according to claim 29, wherein thehigh-cis polybutadiene has a molecular weight adjusted by a compoundselected from (1) hydrogen, (2) a hydrogenated metallic compound and (3)a hydrogenated organometallic compound.
 32. The rubber composition forgolf balls according to claim 31, wherein the hydrogenatedorganometallic compound comprises a dialkyl aluminum hydride.
 33. Therubber composition for golf balls according to claim 29, wherein thehigh-cis polybutadiene comprises a cis-1,4-polybutadiene having 90% ormore of a cis-1,4 structure.